In what scenarios do you want to have a SurfaceInfo with a valid SurfaceID but not other valid fields?

Well, really they're dumb mistakes I made while building the surface synchronization prototype. The parent allocates a new SurfaceID for the child, but the SurfaceLayer corresponding to the child in the parent takes in a SurfaceInfo for the new primary SurfaceInfo. We (me) can naively/accidentally pass in an invalid SurfaceInfo, and so we should probably DCHECK that it's valid in SurfaceLayer.

SurfaceInfos are sent over IPC. I should probably check that they're valid in the StructTraits/ParamTraits. The display compositor sends the window server a SurfaceInfo which is then passed blindly to the parent. The gpu process can in theory be pwn3d and so we should ensure that we're sending valid SurfaceInfos on deseralization.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/9afc576bd3e06d83d6abc870000293b4be9d6132

commit 9afc576bd3e06d83d6abc870000293b4be9d6132
Author: staraz <staraz@chromium.org>
Date: Wed Mar 01 19:39:25 2017

Add cc::SurfaceInfo::is_valid()

SurfaceInfo::is_valid() returns true iff the SurfaceId is valid AND the device
scale factor is non-zero AND the frame size is not empty.

SurfaceInfo::is_valid() replaces obtaining and checking if the SurfaceId of a
SurfaceInfo object is valid. While that is a necessary condition of validity of
a SurfaceInfo, it is technically insufficient.

BUG= 695420 
CQ_INCLUDE_TRYBOTS=master.tryserver.blink:linux_trusty_blink_rel

Review-Url: https://codereview.chromium.org/2720503008
Cr-Commit-Position: refs/heads/master@{#453998}

[modify] https://crrev.com/9afc576bd3e06d83d6abc870000293b4be9d6132/cc/ipc/cc_param_traits.cc
[modify] https://crrev.com/9afc576bd3e06d83d6abc870000293b4be9d6132/cc/ipc/cc_param_traits.h
[modify] https://crrev.com/9afc576bd3e06d83d6abc870000293b4be9d6132/cc/ipc/cc_param_traits_macros.h
[modify] https://crrev.com/9afc576bd3e06d83d6abc870000293b4be9d6132/cc/ipc/cc_param_traits_unittest.cc
[modify] https://crrev.com/9afc576bd3e06d83d6abc870000293b4be9d6132/cc/ipc/surface_info_struct_traits.h
[modify] https://crrev.com/9afc576bd3e06d83d6abc870000293b4be9d6132/cc/layers/surface_layer.cc
[modify] https://crrev.com/9afc576bd3e06d83d6abc870000293b4be9d6132/cc/layers/surface_layer_impl.cc
[modify] https://crrev.com/9afc576bd3e06d83d6abc870000293b4be9d6132/cc/surfaces/surface_info.h
[modify] https://crrev.com/9afc576bd3e06d83d6abc870000293b4be9d6132/cc/trees/layer_tree_host_impl.cc
[modify] https://crrev.com/9afc576bd3e06d83d6abc870000293b4be9d6132/services/ui/ws/frame_generator.cc
[modify] https://crrev.com/9afc576bd3e06d83d6abc870000293b4be9d6132/third_party/WebKit/Source/platform/graphics/CanvasSurfaceLayerBridge.cpp
[modify] https://crrev.com/9afc576bd3e06d83d6abc870000293b4be9d6132/ui/aura/mus/window_port_mus.cc
[modify] https://crrev.com/9afc576bd3e06d83d6abc870000293b4be9d6132/ui/compositor/layer.cc